Escaping from the Tyranny of Body Mass Index

Is Body Mass Index (BMI) dead? That depends on how you’ve been using it. If you’ve been using it to define obesity, then maybe it will soon be dead to you. Today in Obesity, a new commentary and an editorial both call for an end to BMI as the hard and fast definition of obesity.

A Better Definition for Obesity

Simplistic descriptions of obesity have long stated that a BMI of more than 30 defines obesity. But authoritative definitions have always referred back to health. The World Health Organization defines obesity as “abnormal or excessive fat accumulation that may impair health.”

Simplistic use of BMI alone opens up an absurd can of worms. We have endless publications about “healthy obesity,” documenting that some people can be perfectly healthy at a BMI over 30. Likewise, some people have visceral fat that is causing real health problems at a BMI less than 30. That’s skinny obesity.

And then in addition, people argue about the virtues of being fat and fit. Cardiorespiratory fitness is absolutely an important measure of health. A simplistic definition of obesity by BMI alone discounts the importance of fitness for health.

Arya Sharma and Denise Campbell-Scherer offer a simple solution. Define obesity as abnormal or excessive fat accumulation that impairs health. They’ve removed “may” from the WHO definition to put the focus on health.

A Useful Point of Reference

Obesity editors Donna Ryan and Eric Ravussin “fully agree” that BMI should not be the sole criteria for diagnosing obesity. They go on to say that BMI has value for screening and for epidemiology.

To all of this, we say amen. Body Mass Index is useful so long as we don’t make it a tyrant. Size does not define obesity. Adiposity and its effect on health define it.

Click here for the commentary by Sharma and Campbell-Scherer. And here is the editorial by Ryan and Ravussin.

4 Responses to “Escaping from the Tyranny of Body Mass Index”

Pigs might fly. Although of course they will be expected to pay for two seats!

We’ve been saying this for years. Doctors will never stop using it because it’s so easy to measure and calculate. NICE guidelines on weight management from years ago had a section on why BMI was not useful as a measure of health risk at the individual level, before basing their whole guidelines on it. I simply don’t believe it’ll happen.

March 28, 2017 at 7:31 am, Ted said:

Thanks, Angela. If BMI ever fell out of use, we would be missing a whipping boy.

March 28, 2017 at 9:46 am, Allen Browne said:

Health is the issue. But let’s not throw the baby out with the bath water.

A screen is a screen. It should be easy and available. It should be more sensitive than specific.